public void AddConfirmation([DefaultValue("urn:oasis:names:tc:SAML:2.0:cm:bearer")]string method, Uri recipient, int minutes)
        {
            _confirmation = new SubjectConfirmation
            {
                Method = new Uri(method),
            };

            var data = new SubjectConfirmationData
            {
                NotOnOrAfter = new DateTimeOffset(_now.AddMinutes(minutes)),
                Recipient = recipient
            };

            _confirmation.Add(data);

            _response.Subject.Add(_confirmation);
        }